Multi-layered compositions such as permanently bonded laminates are very useful. These multi-layered laminates take advantage of the good properties of each of the individual layers of the laminate. Laminates having good strength, good solvent resistance, good grease resistance and low gas permeability are very desirable and could be formed from a strong layer, a layer that is solvent or grease resistant and a layer that has low gas permeability giving the resulting laminate the desirable overall properties. These laminates have uses in packaging applications such as the packaging of grease covered metallic parts.
Many laminates that are made of independent layers that are destructively bonded together are well known and are generally made of porous substrates and a bonded polymer coating such as a layer of polyethylene bonded to a substrate such as paper. However, laminates using a non-porous substrate such as metal foil or nylon do not generally form permanent bonded layers that are destructive when separated. Thus, these non-porous substrates must be primed with some sort of primer to allow permanent bonding of the polymer to the substrate. Polyethylenes are permanently bonded to non-porous substrates if the substrate is primed with a polyethylene imine primer. Whereas polymers of propylene cannot be bonded to these non-porous substrates without the use of a very unique primer, a chlorinated polypropylene primer. The polypropylene layer in a laminate adds the advantages of excellent grease and solvent-resistance to the laminates, however, producing these polypropylene laminates is expensive due to the cost of the chlorinated polypropylene primer. Additionally, chlorine containing materials are undesirable due to the tendency of forming hydrochloric acid which is very corrosive.
Thus, it would be very desirable to be able to produce inexpensive laminates containing a layer of polypropylene without the use of a chlorinated polypropylene primer.